diff --git a/usr/src/cmd/zpool/zpool_main.c b/usr/src/cmd/zpool/zpool_main.c
index 247865ec..9c19b819 100644
--- a/usr/src/cmd/zpool/zpool_main.c
+++ b/usr/src/cmd/zpool/zpool_main.c
@@ -196,8 +196,8 @@ get_usage(zpool_help_t idx) {
 	case HELP_CLEAR:
 		return (gettext("\tclear <pool> [device]\n"));
 	case HELP_CREATE:
-		return (gettext("\tcreate  [-fn] [-R root] [-m mountpoint] "
-		    "<pool> <vdev> ...\n"));
+		return (gettext("\tcreate [-fn] [-o property=value] ... \n"
+		    "\t    [-m mountpoint] [-R root] <pool> <vdev> ...\n"));
 	case HELP_DESTROY:
 		return (gettext("\tdestroy [-f] <pool>\n"));
 	case HELP_DETACH:
@@ -445,6 +445,52 @@ print_vdev_tree(zpool_handle_t *zhp, const char *name, nvlist_t *nv, int indent,
 	}
 }
 
+/*
+ * Add a property pair (name, string-value) into a property nvlist.
+ */
+static int
+add_prop_list(const char *propname, char *propval, nvlist_t **props,
+    boolean_t poolprop)
+{
+	zpool_prop_t prop = ZPOOL_PROP_INVAL;
+	zfs_prop_t fprop;
+	nvlist_t *proplist;
+	const char *normnm;
+	char *strval;
+
+	if (*props == NULL &&
+	    nvlist_alloc(props, NV_UNIQUE_NAME, 0) != 0) {
+		(void) fprintf(stderr,
+		    gettext("internal error: out of memory\n"));
+		return (1);
+	}
+
+	proplist = *props;
+
+	if (poolprop) {
+		if ((prop = zpool_name_to_prop(propname)) == ZPOOL_PROP_INVAL) {
+			(void) fprintf(stderr, gettext("property '%s' is "
+			    "not a valid pool property\n"), propname);
+			return (2);
+		}
+		normnm = zpool_prop_to_name(prop);
+	} else {
+		if ((fprop = zfs_name_to_prop(propname)) != ZFS_PROP_INVAL) {
+			normnm = zfs_prop_to_name(fprop);
+		} else {
+			normnm = propname;
+		}
+	}
+
+	if (nvlist_add_string(proplist, normnm, propval) != 0) {
+		(void) fprintf(stderr, gettext("internal "
+		    "error: out of memory\n"));
+		return (1);
+	}
+
+	return (0);
+}
+
 /*
  * zpool add [-fn] <pool> <vdev> ...
  *
@@ -513,7 +559,7 @@ zpool_do_add(int argc, char **argv)
 	}
 
 	/* pass off to get_vdev_spec for processing */
-	nvroot = make_root_vdev(zhp, force, !force, B_FALSE, argc, argv);
+	nvroot = make_root_vdev(zhp, NULL, force, !force, B_FALSE, argc, argv);
 	if (nvroot == NULL) {
 		zpool_close(zhp);
 		return (1);
@@ -589,7 +635,7 @@ zpool_do_remove(int argc, char **argv)
 }
 
 /*
- * zpool create [-fn] [-R root] [-m mountpoint] <pool> <dev> ...
+ * zpool create [-fn] [-o property=value] ... [-R root] [-m mountpoint] <pool> <dev> ...
  *
  *	-f	Force creation, even if devices appear in use
  *	-n	Do not create the pool, but display the resulting layout if it
@@ -597,6 +643,7 @@ zpool_do_remove(int argc, char **argv)
  *      -R	Create a pool under an alternate root
  *      -m	Set default mountpoint for the root dataset.  By default it's
  *      	'/<pool>'
+ *      -o	Set property=value.
  *
  * Creates the named pool according to the given vdev specification.  The
  * bulk of the vdev processing is done in get_vdev_spec() in zpool_vdev.c.  Once
@@ -616,9 +663,11 @@ zpool_do_create(int argc, char **argv)
 	char *mountpoint = NULL;
 	nvlist_t **child;
 	uint_t children;
+	nvlist_t *props = NULL;
+	char *propval = NULL;
 
 	/* check options */
-	while ((c = getopt(argc, argv, ":fnR:m:")) != -1) {
+	while ((c = getopt(argc, argv, ":fnR:m:o:")) != -1) {
 		switch (c) {
 		case 'f':
 			force = B_TRUE;
@@ -632,6 +681,17 @@ zpool_do_create(int argc, char **argv)
 		case 'm':
 			mountpoint = optarg;
 			break;
+		case 'o':
+			if ((propval = strchr(optarg, '=')) == NULL) {
+				(void) fprintf(stderr, gettext("missing "
+				    "'=' for -o option\n"));
+				usage(B_FALSE);
+			}
+			*propval = '\0';
+			propval++;
+			if (add_prop_list(optarg, propval, &props, B_TRUE))
+				usage(B_FALSE);
+			break;
 		case ':':
 			(void) fprintf(stderr, gettext("missing argument for "
 			    "'%c' option\n"), optopt);
@@ -672,7 +732,7 @@ zpool_do_create(int argc, char **argv)
 	}
 
 	/* pass off to get_vdev_spec for bulk processing */
-	nvroot = make_root_vdev(NULL, force, !force, B_FALSE, argc - 1,
+	nvroot = make_root_vdev(NULL, props, force, !force, B_FALSE, argc - 1,
 	    argv + 1);
 	if (nvroot == NULL)
 		return (1);
@@ -766,6 +826,12 @@ zpool_do_create(int argc, char **argv)
 		ret = 0;
 	} else {
 		ret = 1;
+		/*
+		 * Add other properties not describing the vdev topology
+		 */
+		if (props)
+			nvlist_add_nvlist(nvroot, ZPOOL_CONFIG_PROPS, props);
+
 		/*
 		 * Hand off to libzfs.
 		 */
@@ -2322,7 +2388,7 @@ zpool_do_attach_or_replace(int argc, char **argv, int replacing)
 		return (1);
 	}
 
-	nvroot = make_root_vdev(zhp, force, B_FALSE, replacing, argc, argv);
+	nvroot = make_root_vdev(zhp, NULL, force, B_FALSE, replacing, argc, argv);
 	if (nvroot == NULL) {
 		zpool_close(zhp);
 		return (1);
diff --git a/usr/src/cmd/zpool/zpool_util.h b/usr/src/cmd/zpool/zpool_util.h
index 2a1aca03..f4e2c154 100644
--- a/usr/src/cmd/zpool/zpool_util.h
+++ b/usr/src/cmd/zpool/zpool_util.h
@@ -47,7 +47,7 @@ uint_t num_logs(nvlist_t *nv);
  * Virtual device functions
  */
 
-nvlist_t *make_root_vdev(zpool_handle_t *zhp, int force, int check_rep,
+nvlist_t *make_root_vdev(zpool_handle_t *zhp, nvlist_t *props, int force, int check_rep,
     boolean_t isreplace, int argc, char **argv);
 
 /*
diff --git a/usr/src/cmd/zpool/zpool_vdev.c b/usr/src/cmd/zpool/zpool_vdev.c
index 63b93a19..d8a8c5e7 100644
--- a/usr/src/cmd/zpool/zpool_vdev.c
+++ b/usr/src/cmd/zpool/zpool_vdev.c
@@ -413,7 +413,7 @@ is_whole_disk(const char *arg)
  * 	xxx		Shorthand for /dev/dsk/xxx
  */
 static nvlist_t *
-make_leaf_vdev(const char *arg, uint64_t is_log)
+make_leaf_vdev(nvlist_t *props, const char *arg, uint64_t is_log)
 {
 	char path[MAXPATHLEN];
 	struct stat statbuf;
@@ -538,6 +538,20 @@ make_leaf_vdev(const char *arg, uint64_t is_log)
 		(void) close(fd);
 	}
 
+	if (props != NULL) {
+
+		uint64_t ashift = 0;
+		char *value = NULL;
+
+		if (nvlist_lookup_string(props,
+		    zpool_prop_to_name(ZPOOL_PROP_ASHIFT), &value) == 0)
+			zfs_nicestrtonum(NULL, value, &ashift);
+
+		if (ashift > 0)
+			verify(nvlist_add_uint64(vdev, ZPOOL_CONFIG_ASHIFT,
+			    ashift) == 0);
+	}
+
 	return (vdev);
 }
 
@@ -1158,7 +1172,7 @@ is_grouping(const char *type, int *mindev)
  * because the program is just going to exit anyway.
  */
 nvlist_t *
-construct_spec(int argc, char **argv)
+construct_spec(nvlist_t *props, int argc, char **argv)
 {
 	nvlist_t *nvroot, *nv, **top, **spares;
 	int t, toplevels, mindev, nspares, nlogs;
@@ -1234,7 +1248,7 @@ construct_spec(int argc, char **argv)
 				    children * sizeof (nvlist_t *));
 				if (child == NULL)
 					zpool_no_memory();
-				if ((nv = make_leaf_vdev(argv[c], B_FALSE))
+				if ((nv = make_leaf_vdev(props, argv[c], B_FALSE))
 				    == NULL)
 					return (NULL);
 				child[children - 1] = nv;
@@ -1279,7 +1293,7 @@ construct_spec(int argc, char **argv)
 			 * We have a device.  Pass off to make_leaf_vdev() to
 			 * construct the appropriate nvlist describing the vdev.
 			 */
-			if ((nv = make_leaf_vdev(argv[0], is_log)) == NULL)
+			if ((nv = make_leaf_vdev(props, argv[0], is_log)) == NULL)
 				return (NULL);
 			if (is_log)
 				nlogs++;
@@ -1342,7 +1356,7 @@ construct_spec(int argc, char **argv)
  * added, even if they appear in use.
  */
 nvlist_t *
-make_root_vdev(zpool_handle_t *zhp, int force, int check_rep,
+make_root_vdev(zpool_handle_t *zhp, nvlist_t *props, int force, int check_rep,
     boolean_t isreplacing, int argc, char **argv)
 {
 	nvlist_t *newroot;
@@ -1354,7 +1368,7 @@ make_root_vdev(zpool_handle_t *zhp, int force, int check_rep,
 	 * that we have a valid specification, and that all devices can be
 	 * opened.
 	 */
-	if ((newroot = construct_spec(argc, argv)) == NULL)
+	if ((newroot = construct_spec(props, argc, argv)) == NULL)
 		return (NULL);
 
 	if (zhp && ((poolconfig = zpool_get_config(zhp, NULL)) == NULL))
diff --git a/usr/src/common/zfs/zfs_prop.c b/usr/src/common/zfs/zfs_prop.c
index 4bb2d3d7..3d30d64b 100644
--- a/usr/src/common/zfs/zfs_prop.c
+++ b/usr/src/common/zfs/zfs_prop.c
@@ -70,7 +70,14 @@
 typedef enum {
 	PROP_DEFAULT,
 	PROP_READONLY,
-	PROP_INHERIT
+	PROP_INHERIT,
+	/*
+	 * ONETIME properties are a sort of conglomeration of READONLY
+	 * and INHERIT. They can be set only during object creation,
+	 * after that they are READONLY. If not explicitly set during
+	 * creation, they can be inherited.
+	 */
+	PROP_ONETIME
 } prop_attr_t;
 
 typedef struct zfs_index {
@@ -326,10 +333,15 @@ zfs_prop_init(void)
 	register_number(ZFS_PROP_COMPRESSRATIO, "compressratio", 0,
 	    PROP_READONLY, ZFS_TYPE_ANY,
 	    "<1.00x or higher if compressed>", "RATIO");
+
+	/* readonly onetime number properties */
+	register_number(ZPOOL_PROP_ASHIFT, "ashift", 0, PROP_ONETIME,
+	    ZFS_TYPE_POOL, "<ashift, 9-17, or 0=default>", "ASHIFT");
 	register_number(ZFS_PROP_VOLBLOCKSIZE, "volblocksize", 8192,
-	    PROP_READONLY,
+	    PROP_ONETIME,
 	    ZFS_TYPE_VOLUME, "512 to 128k, power of 2",	"VOLBLOCK");
 
+
 	/* default number properties */
 	register_number(ZFS_PROP_QUOTA, "quota", 0, PROP_DEFAULT,
 	    ZFS_TYPE_FILESYSTEM, "<size> | none", "QUOTA");
@@ -616,7 +628,17 @@ zpool_prop_default_numeric(zpool_prop_t prop)
 int
 zfs_prop_readonly(zfs_prop_t prop)
 {
-	return (zfs_prop_table[prop].pd_attr == PROP_READONLY);
+	return (zfs_prop_table[prop].pd_attr == PROP_READONLY ||
+	    zfs_prop_table[prop].pd_attr == PROP_ONETIME);
+}
+
+/*
+ * Returns TRUE if the property is only allowed to be set once.
+ */
+boolean_t
+zfs_prop_setonce(zfs_prop_t prop)
+{
+	return (zfs_prop_table[prop].pd_attr == PROP_ONETIME);
 }
 
 /*
@@ -645,7 +667,8 @@ zpool_prop_to_name(zpool_prop_t prop)
 int
 zfs_prop_inheritable(zfs_prop_t prop)
 {
-	return (zfs_prop_table[prop].pd_attr == PROP_INHERIT);
+	return (zfs_prop_table[prop].pd_attr == PROP_INHERIT ||
+	    zfs_prop_table[prop].pd_attr == PROP_ONETIME);
 }
 
 /*
diff --git a/usr/src/lib/libzfs/common/libzfs_dataset.c b/usr/src/lib/libzfs/common/libzfs_dataset.c
index 58abeb60..5f214d01 100644
--- a/usr/src/lib/libzfs/common/libzfs_dataset.c
+++ b/usr/src/lib/libzfs/common/libzfs_dataset.c
@@ -694,7 +694,7 @@ bootfs_poolname_valid(char *pool, char *bootfs)
  */
 nvlist_t *
 zfs_validate_properties(libzfs_handle_t *hdl, zfs_type_t type, char *pool_name,
-    nvlist_t *nvl, uint64_t zoned, zfs_handle_t *zhp, const char *errbuf)
+    nvlist_t *nvl, uint64_t zoned, zfs_handle_t *zhp, const char *errbuf, boolean_t creating)
 {
 	nvpair_t *elem;
 	const char *propname;
@@ -780,7 +780,7 @@ zfs_validate_properties(libzfs_handle_t *hdl, zfs_type_t type, char *pool_name,
 		}
 
 		if (zfs_prop_readonly(prop) &&
-		    (prop != ZFS_PROP_VOLBLOCKSIZE || zhp != NULL)) {
+		    (!zfs_prop_setonce(prop) || (creating == B_FALSE))) {
 			zfs_error_aux(hdl,
 			    dgettext(TEXT_DOMAIN, "'%s' is readonly"),
 			    propname);
@@ -1036,6 +1036,26 @@ zfs_validate_properties(libzfs_handle_t *hdl, zfs_type_t type, char *pool_name,
 
 			break;
 #endif /* !__APPLE__ */
+
+		case ZPOOL_PROP_ASHIFT:
+			if (creating == B_FALSE) {
+				zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+				    "property '%s' can only be set at "
+				    "creation time"), propname);
+				(void) zfs_error(hdl, EZFS_BADPROP, errbuf);
+				goto error;
+			}
+
+			if (intval != 0 && (intval < 9 || intval > 17)) {
+				zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+				    "property '%s' number %d is invalid."),
+				    propname, intval);
+				(void) zfs_error(hdl, EZFS_BADPROP, errbuf);
+				goto error;
+			}
+
+			break;
+
 		case ZPOOL_PROP_BOOTFS:
 			/*
 			 * bootfs property value has to be a dataset name and
@@ -1848,7 +1868,7 @@ zfs_prop_set(zfs_handle_t *zhp, const char *propname, const char *propval)
 	}
 
 	if ((realprops = zfs_validate_properties(hdl, zhp->zfs_type, NULL, nvl,
-	    zfs_prop_get_int(zhp, ZFS_PROP_ZONED), zhp, errbuf)) == NULL)
+	    zfs_prop_get_int(zhp, ZFS_PROP_ZONED), zhp, errbuf, B_FALSE)) == NULL)
 		goto error;
 	nvlist_free(nvl);
 	nvl = realprops;
@@ -2835,7 +2855,7 @@ zfs_create(libzfs_handle_t *hdl, const char *path, zfs_type_t type,
 		zc.zc_objset_type = DMU_OST_ZFS;
 
 	if (props && (props = zfs_validate_properties(hdl, type, NULL, props,
-	    zoned, NULL, errbuf)) == 0)
+	    zoned, NULL, errbuf, B_TRUE)) == 0)
 		return (-1);
 
 	if (type == ZFS_TYPE_VOLUME) {
@@ -3120,7 +3140,7 @@ zfs_clone(zfs_handle_t *zhp, const char *target, nvlist_t *props)
 
 	if (props) {
 		if ((props = zfs_validate_properties(hdl, type, NULL, props,
-		    zoned, zhp, errbuf)) == NULL)
+		    zoned, zhp, errbuf, B_TRUE)) == NULL)
 			return (-1);
 
 		if (zcmd_write_src_nvlist(hdl, &zc, props, NULL) != 0) {
diff --git a/usr/src/lib/libzfs/common/libzfs_impl.h b/usr/src/lib/libzfs/common/libzfs_impl.h
index ed575c87..e401eda7 100644
--- a/usr/src/lib/libzfs/common/libzfs_impl.h
+++ b/usr/src/lib/libzfs/common/libzfs_impl.h
@@ -119,7 +119,7 @@ zfs_prop_t zfs_prop_iter_common(zfs_prop_f, void *, zfs_type_t, boolean_t,
 zfs_prop_t zfs_name_to_prop_common(const char *, zfs_type_t);
 
 nvlist_t *zfs_validate_properties(libzfs_handle_t *, zfs_type_t, char *,
-	nvlist_t *, uint64_t, zfs_handle_t *zhp, const char *errbuf);
+	nvlist_t *, uint64_t, zfs_handle_t *zhp, const char *errbuf, boolean_t creating);
 
 typedef struct prop_changelist prop_changelist_t;
 
diff --git a/usr/src/lib/libzfs/common/libzfs_pool.c b/usr/src/lib/libzfs/common/libzfs_pool.c
index 3a6471fc..b30c431f 100644
--- a/usr/src/lib/libzfs/common/libzfs_pool.c
+++ b/usr/src/lib/libzfs/common/libzfs_pool.c
@@ -399,6 +399,7 @@ zpool_create(libzfs_handle_t *hdl, const char *pool, nvlist_t *nvroot,
 {
 	zfs_cmd_t zc = { 0 };
 	char msg[1024];
+	nvlist_t *props = NULL;
 
 	(void) snprintf(msg, sizeof (msg), dgettext(TEXT_DOMAIN,
 	    "cannot create '%s'"), pool);
@@ -410,6 +411,24 @@ zpool_create(libzfs_handle_t *hdl, const char *pool, nvlist_t *nvroot,
 		return (zfs_error_fmt(hdl, EZFS_BADPATH,
 		    dgettext(TEXT_DOMAIN, "bad alternate root '%s'"), altroot));
 
+	/*
+	 * Process additional properties not (directly) describing the
+	 * vdev tree.
+	 */
+
+	if (nvlist_lookup_nvlist(nvroot, ZPOOL_CONFIG_PROPS, &props) == 0) {
+		char errbuf[1024];
+		nvlist_t *newprops = zfs_validate_properties(hdl, ZFS_TYPE_POOL,
+		    pool, props, 0, NULL, errbuf, B_TRUE);
+		nvlist_remove(nvroot, ZPOOL_CONFIG_PROPS, DATA_TYPE_NVLIST);
+		if (newprops) {
+			nvlist_add_nvlist(nvroot, ZPOOL_CONFIG_PROPS, newprops);
+		} else {
+			return(zfs_error(hdl, EZFS_BADPROP, msg));
+		}
+		nvlist_free(newprops);
+	}
+
 	if (zcmd_write_src_nvlist(hdl, &zc, nvroot, NULL) != 0)
 		return (-1);
 
@@ -2228,7 +2247,7 @@ zpool_set_prop(zpool_handle_t *zhp, const char *propname, const char *propval)
 	}
 
 	if ((realprops = zfs_validate_properties(zhp->zpool_hdl, ZFS_TYPE_POOL,
-	    zhp->zpool_name, nvl, 0, NULL, errbuf)) == NULL) {
+	    zhp->zpool_name, nvl, 0, NULL, errbuf, B_FALSE)) == NULL) {
 		nvlist_free(nvl);
 		return (-1);
 	}
@@ -2267,6 +2286,7 @@ zpool_get_prop_int(zpool_handle_t *zhp, zpool_prop_t prop)
 
 	switch (prop) {
 	case ZPOOL_PROP_AUTOREPLACE:
+	case ZPOOL_PROP_ASHIFT:
 		if (nvlist_lookup_nvlist(zhp->zpool_props,
 		    zpool_prop_to_name(prop), &nvp) != 0) {
 			value = zpool_prop_default_numeric(prop);
@@ -2347,6 +2367,21 @@ zpool_get_prop(zpool_handle_t *zhp, zpool_prop_t prop, char *propbuf,
 		(void) strlcpy(propbuf, value ? "on" : "off", proplen);
 		break;
 
+	case ZPOOL_PROP_ASHIFT:
+		if (nvlist_lookup_nvlist(zhp->zpool_props,
+		    zpool_prop_to_name(prop), &nvp) != 0) {
+			value = zpool_prop_default_numeric(prop);
+			src = ZFS_SRC_DEFAULT;
+		} else {
+			VERIFY(nvlist_lookup_uint64(nvp,
+			    ZFS_PROP_SOURCE, &value) == 0);
+			src = value;
+			VERIFY(nvlist_lookup_uint64(nvp, ZFS_PROP_VALUE,
+			    &value) == 0);
+		}
+		(void) snprintf(propbuf, proplen, "%llu", value);
+		break;
+  
 	default:
 		return (-1);
 	}
diff --git a/usr/src/uts/common/fs/zfs/dsl_prop.c b/usr/src/uts/common/fs/zfs/dsl_prop.c
index e814fe27..3fd2fae9 100644
--- a/usr/src/uts/common/fs/zfs/dsl_prop.c
+++ b/usr/src/uts/common/fs/zfs/dsl_prop.c
@@ -44,8 +44,13 @@ dodefault(const char *propname, int intsz, int numint, void *buf)
 {
 	zfs_prop_t prop;
 
+	/*
+	 * The setonce properties are read-only, BUT they still
+	 * have a default value that can be used as the initial
+	 * value.
+	 */
 	if ((prop = zfs_name_to_prop(propname)) == ZFS_PROP_INVAL ||
-	    zfs_prop_readonly(prop))
+	    (zfs_prop_readonly(prop) && !zfs_prop_setonce(prop)))
 		return (ENOENT);
 
 	if (zfs_prop_get_type(prop) == PROP_TYPE_STRING) {
diff --git a/usr/src/uts/common/fs/zfs/spa.c b/usr/src/uts/common/fs/zfs/spa.c
index 33e63251..7686b15b 100644
--- a/usr/src/uts/common/fs/zfs/spa.c
+++ b/usr/src/uts/common/fs/zfs/spa.c
@@ -1138,6 +1138,7 @@ spa_create(const char *pool, nvlist_t *nvroot, const char *altroot,
 	uint64_t txg = TXG_INITIAL;
 	nvlist_t **spares;
 	uint_t nspares;
+	nvlist_t *props = 0;
 
 	/*
 	 * If this pool already exists, return failure.
@@ -1272,6 +1273,21 @@ spa_create(const char *pool, nvlist_t *nvroot, const char *altroot,
 
 	mutex_exit(&spa_namespace_lock);
 
+	/*
+	 * Process additional properties not set diectly in above call.
+	 */
+
+	if (nvlist_lookup_nvlist(nvroot, ZPOOL_CONFIG_PROPS, &props) == 0) {
+		/*
+		 * Remove properties already set above
+		 */
+		nvlist_remove(nvroot, zpool_prop_to_name(ZPOOL_PROP_DELEGATION), DATA_TYPE_UINT64);
+		nvlist_remove(nvroot, zpool_prop_to_name(ZPOOL_PROP_BOOTFS), DATA_TYPE_UINT64);
+		
+		/* apply porperties. */
+		spa_set_props(spa, props);
+	}
+
 	return (0);
 }
 
@@ -3014,6 +3030,15 @@ spa_sync_props(void *arg1, void *arg2, cred_t *cr, dmu_tx_t *tx)
 			    zpool_prop_to_name(ZPOOL_PROP_AUTOREPLACE), 8, 1,
 			    &intval, tx) == 0);
 			break;
+
+		case ZPOOL_PROP_ASHIFT:
+			VERIFY(nvlist_lookup_uint64(nvp,
+			    nvpair_name(nvpair), &intval) == 0);
+			VERIFY(zap_update(mos,
+			    spa->spa_pool_props_object,
+			    zpool_prop_to_name(ZPOOL_PROP_ASHIFT), 8, 1,
+			    &intval, tx) == 0);
+			break;
 		}
 		spa_history_internal_log(LOG_POOL_PROPSET,
 		    spa, tx, cr, "%s %lld %s",
diff --git a/usr/src/uts/common/fs/zfs/zfs_ioctl.c b/usr/src/uts/common/fs/zfs/zfs_ioctl.c
index b28bf952..a692e881 100644
--- a/usr/src/uts/common/fs/zfs/zfs_ioctl.c
+++ b/usr/src/uts/common/fs/zfs/zfs_ioctl.c
@@ -1535,6 +1535,15 @@ zfs_ioc_pool_set_props(zfs_cmd_t *zc)
 			objnum = dmu_objset_id(os);
 			dmu_objset_close(os);
 			break;
+
+		case ZPOOL_PROP_ASHIFT:
+			/* 
+			 * Property can only be set at pool create time, and
+			 * that code path does not go through this function.
+			 * So unconditionally fail here.
+			 */
+			error = EPERM;
+			break;
 		}
 
 		if (error)
diff --git a/usr/src/uts/common/sys/fs/zfs.h b/usr/src/uts/common/sys/fs/zfs.h
index 2dbb168f..4fed3e99 100644
--- a/usr/src/uts/common/sys/fs/zfs.h
+++ b/usr/src/uts/common/sys/fs/zfs.h
@@ -106,6 +106,7 @@ typedef enum {
 	ZPOOL_PROP_DELEGATION,
 	ZFS_PROP_VERSION,
 	ZPOOL_PROP_NAME,
+	ZPOOL_PROP_ASHIFT,
 	ZFS_NUM_PROPS
 } zfs_prop_t;
 
@@ -283,6 +284,9 @@ extern zpool_prop_t zpool_prop_iter(zpool_prop_f, void *);
 #define	ZPOOL_CONFIG_DEGRADED		"degraded"
 #define	ZPOOL_CONFIG_REMOVED		"removed"
 
+/* Extra properties passed to spa_create. */
+#define ZPOOL_CONFIG_PROPS		"props"
+
 #define	VDEV_TYPE_ROOT			"root"
 #define	VDEV_TYPE_MIRROR		"mirror"
 #define	VDEV_TYPE_REPLACING		"replacing"